Process and system for heating or cooling streams for a divided distillation column

ABSTRACT

One exemplary embodiment can be a system for separating a plurality of naphtha components. The system can include a column, an overhead condenser, and a side condenser. Generally, the column includes a dividing imperforate wall with one surface facing a feed and another surface facing at least one side stream. Typically, the wall extends a significant portion of the column height to divide the portion into at least two substantially vertical, parallel contacting sections. Typically, the overhead condenser receives an overhead stream including a light naphtha from the column. Usually, a side condenser receives a process stream from the column and returns the stream to the column to facilitate separation. A cooling stream may pass through the overhead condenser and then the side condenser.

FIELD OF THE INVENTION

This invention generally relates to a divided distillation column, andcondensing and heating duties relating thereto.

DESCRIPTION OF THE RELATED ART

In some instances, a dividing wall column can be more efficient forseparating three or more products from a feed. Particularly, in someinstances a dividing wall column can be used instead of two or moreconventional distillation columns. Thus, the single dividing wall columncan provide energy and capital savings as compared to a plurality ofconventional columns that are utilized to obtain the same separation.

However, an individual dividing wall column typically requires all ofthe heating supplied at a maximum temperature and all of the coolingsupplied at a minimum temperature. Generally, providing these conditionsat high and low temperatures requires expensive utilities, such as highpressure steam, available in a refinery or a chemical manufacturingfacility. On the other hand, a series of conventional distillationcolumns can have intermediate duties supplied, which can be provided bylower cost utilities, such as medium pressure steam, which can be lessexpensive. Consequently, efficiently utilizing heating and/or coolingstreams to obtain the requisite duty requirements of a dividing wallcolumn would be highly desirable.

SUMMARY OF THE INVENTION

One exemplary embodiment can be a system for separating a plurality ofnaphtha components. The system can include a column, an overheadcondenser, and a side condenser. Generally, the column includes adividing imperforate wall with one surface facing a feed and anothersurface facing at least one side stream. Usually, the wall extends asignificant portion of the column height to divide the portion into atleast two substantially vertical, parallel contacting sections.Typically, the overhead condenser receives an overhead stream includinga light naphtha from the column. Usually, a side condenser receives aprocess stream from the column and returns the stream to the column tofacilitate separation. A cooling stream may pass through the overheadcondenser and then the side condenser.

Another embodiment can be a system for separating a plurality of naphthacomponents that may include a first column and a second column.Generally, the first column includes a dividing imperforate wall withone surface facing a feed and another surface facing a side stream, areboiler, and a side reboiler. Usually, the wall extends a significantportion of the column height to divide the portion into at least twosubstantially vertical, parallel contacting sections. Typically, thesecond column is non-divided and communicates with the first column soas to provide a feed to or receive a feed from the first column. Aheating stream can pass through the reboiler and the side reboiler.

Yet a further embodiment may be a process for utilizing streams for aplurality of vessels communicating with a divided distillation column.The process can include passing a heating stream through a reboiler andthe same or a different heating stream through a side reboiler to reducethe duty required in the reboiler of the divided distillation column.Typically, the divided distillation column produces at least two of alight naphtha, a medium naphtha, an aromatic naphtha, and a heavynaphtha.

Thus, the embodiments disclosed herein can provide mechanisms forefficiently providing increased reboiling and condensing duties. As anexample, a stream can be withdrawn from the column to a side reboiler,and utilizing a lower temperature steam or a process stream can reducethe amount of high temperature steam required for a bottom reboiler ofthe column. As a consequence, the embodiments disclosed herein canprovide greater energy efficiency to further reduce the operating costsof a dividing wall column.

DEFINITIONS

As used herein, the term “stream” can be a stream including varioushydrocarbon molecules, such as straight-chain, branched, or cyclicalkanes, alkenes, alkadienes, and alkynes, and optionally othersubstances, such as gases, e.g., hydrogen, or impurities, such as heavymetals, and sulfur and nitrogen compounds. The stream can also includearomatic and non-aromatic hydrocarbons. Moreover, the hydrocarbonmolecules may be abbreviated C1, C2, C3 . . . Cn where “n” representsthe number of carbon atoms in the one or more hydrocarbon molecules.

As used herein, the term “zone” can refer to an area including one ormore equipment items and/or one or more sub-zones. Equipment items caninclude one or more reactors or reactor vessels, heaters, exchangers,pipes, pumps, compressors, and controllers. Additionally, an equipmentitem, such as a reactor, dryer, or vessel, can further include one ormore zones or sub-zones.

As used herein, the term “dividing wall column” generally means a columnincluding a substantially fluid tight vertical wall extending through asignificant portion of the column's height and located in a centralportion of the column. Thus, a central portion of the column can bedivided into at least two vertical, parallel vapor-liquid contactingsections. The top and bottom of the wall terminate in the column at apoint distant from the respective end of the column such that there isopen communication across the column interior at the top and bottom ofthe dividing wall.

As used herein, the term “non-divided column” generally means a columnabsent a dividing wall positioned substantially vertically within thecolumn dividing a central portion into at least two vertical, parallelvapor-liquid contacting sections.

As used herein, the term “vapor” can mean a gas or a dispersion that mayinclude or consist of one or more hydrocarbons.

As used herein, the term “naphtha components” generally means one ormore hydrocarbons with not less than about 10%, by weight, distillingbelow about 175° C. and not less than about 95%, by weight, distillingbelow about 240° C. in accordance with ASTM-D86-08.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic depiction of one exemplary system with a singledividing wall column producing three products.

FIG. 2 is a schematic depiction of another exemplary system of a singledividing wall column producing four products.

FIG. 3 is a schematic depiction of an exemplary system including aplurality of columns.

DETAILED DESCRIPTION

Referring to FIG. 1, a system 10 can include a column 100, which can bea first column 100. The column 100 can have a dividing imperforate wall110. Generally, the column 100 can receive a feed 200 and produce anoverhead stream 210, at least one side stream 270, and a bottom stream280. Typically, one surface 114 of the imperforate wall 110 can face thefeed 200 while another surface 116 can face the at least one side stream270. Typically, a significant portion 122 of the column height 126 istaken by the imperforate wall 110. Generally, the imperforate wall 110divides the column 100 into at least two vertical, parallel contactingsections 130, namely a first contacting section 134 and a secondcontacting section 138.

The embodiments as described herein can utilize a dividing wall columneither in combination with a non-divided column or alone to produce atleast three or four products. That is, the vapor leaving the top of eachdivided section and the liquid leaving the bottom of each dividedsection can flow into a common section and be admixed. Each sectionoften contains fractionation trays and/or packing intended to promoteseparation. The feed stream to the column can enter on a first receivingside of a dividing wall section of the column. Alternatively, the feedmay enter near the bottom of the receiving section. Exemplary dividingwall columns are disclosed in, e.g., U.S. Pat. No. 6,551,465 B1 and U.S.Pat. No. 6,558,515 B1.

Typically, these product streams can include at least one of a lightnaphtha (LN), a medium naphtha (MN), an aromatics naphtha (ARN), a heavynaphtha (HN), or a combination thereof. The boiling points (BP) and trueboiling points (TBP) as determined by ASTM D2892-05 are depicted in thefollowing table:

TABLE 1 Product Stream BP (° C.) TBP 10 (° C.) TBP 90 (° C.) LN 20-80 61MN  80-150 56 102 ARN 150-215 102 158 HN at least about 215 162

The column 100 can also include an overhead condenser 140, a receiver150, a side condenser 160, a reboiler 170, and a side reboiler 180.Generally, the side condenser 160 and/or side reboiler 180 can provideadditional duty capacity to cool or heat the requisite streams.Particularly, the side condenser 160 can be at a point above the feed200 and the at least one side stream 270 and the bottom stream 280. Inaddition, the side reboiler 180 can provide additional duty and anintermediate temperature level below the feed and product stages.Although both a side condenser 160 and a side reboiler 180 are depicted,it should be understood that only one of these devices may beincorporated into the column 100. In addition, while a side condenser160 is depicted above the dividing wall 110, it should be noted that theside condenser 160 could be located at a point above the feed 200 oneither the feed side 200 or the product side of the wall 110, but abovethe side stream 270. Similarly, the side reboiler 180 could be locatedat a position on the feed side or product side of the wall 110 below thefeed 200 and above the bottom stream 280.

The duty for the side condenser 160 can be provided by cooling utilitiesusing any suitable fluid, such as water, or optionally be used togenerate utilities such as steam or hot oil, or heating a processstream. The duty for a side reboiler 180 can be provided by utilitiessuch as steam or hot oil, or by a process stream. Generally, it is alsobeneficial to use multiple reboiling stages or condensing stages with acombination of process streams and utility streams.

In this exemplary embodiment, an overhead stream 210 can pass throughthe overhead condenser 140 and then to the receiver 150. A portion of alight naphtha product 218 can be provided back to the column as a reflux214. To provide additional duty, a process stream or side draw 220 canbe withdrawn from the column 100, passed through the side condenser 160to be cooled, and returned. A cooling stream 230 can pass or cascadethrough the overhead condenser 140 and the side condenser 160. In thismanner, the cooling stream 230 can be water, such as cooling water, usedfirst to cool the overhead stream 210 and then the side draw 220. Inthis manner, the same utility stream 230 can be used to cool two processstreams to provide additional cooling duty for the column 100.

Below the side stream 270, which is typically a medium naphtha product,a bottom stream 280 can be withdrawn from the column. Usually, a portionis a bottom product 288, typically a heavy naphtha, with another portionas a return 284. The return 284 passes through the reboiler 170. Thereboiler can use any suitable heat source, such as a furnace, highpressure stream, or another process stream. In addition, another processstream or side draw 250 can receive additional heating duty. Typically,the side draw 250 is withdrawn from the column 100 above the bottomstream 280 and below the side stream 270, passed through the sidereboiler 180, and returned. The side reboiler 180 can be located anysuitable elevation on the column 100, such as about half-way between thebottom of the dividing wall 110 and the bottom tray of the column 100.Similarly, as described above for the condensers 140 and 160, a heatingstream 260 can pass through the reboiler 170 and then the side reboiler180. Generally, this heating stream 260 can be any suitable heatingstream, such as a high pressure steam, a medium pressure steam, a lightcycle oil, or another process stream. As an example, the heating stream260 can have an inlet temperature of the reboiler 170 of about 200-about220° C., an outlet temperature of the reboiler 170 of about 180-about200° C., and an outlet temperature of the side reboiler 180 of about165-about 185° C.

As such, utilizing the heating stream 260 through both the reboiler 170and the side reboiler 180 can allow the use of one heating stream toprovide additional heat duty to the column 100.

Another version of the system 10 is depicted in FIG. 2. Particularly,the column 100 can receive a feed 300 and provide an overhead stream 310including a light naphtha, a plurality of side streams 370, namely afirst side stream 374 including a medium naphtha, and second side stream378 including an aromatic naphtha, and a bottom stream 380 including aheavy naphtha. Generally, the feed 300 can enter the column 100 and intothe area defined by the dividing wall 110. The lighter material can risefrom the column 100 and exit as the overhead stream 310, pass throughthe overhead condenser 140 and into the receiver 150. Generally, aportion can be obtained as a light naphtha product 318 with another partreturned as a reflux 314. In addition, a side draw 320 can be withdrawnfrom the column 100, passed through the side condenser 160, andreturned. A cooling stream 330 can pass through the overhead condenser140 and then the side condenser 160 for providing cooling duty. Thecooling stream 330 can be any suitable stream, as described above.

The bottom stream 380 can provide a heavy naphtha product 388 with aportion as a return 384. The return 384 can pass through the reboiler170 before providing heat to the bottom of the column 100. Another sidedraw 350 can pass through the side reboiler 180 before being returned tothe column 100. Typically, the reboiler 170 and the side reboiler 180receive a heating stream 360. The heating stream 360 can be any suitablestream, as described above. In this manner, one utility stream canprovide the requisite cooling duty and another process stream canprovide the requisite heating duty for the column 100. This efficientutilization of such process streams can save energy costs.

Another exemplary version of a system 10 is depicted in FIG. 3.Particularly, the column 100 is placed in series with a non-dividedcolumn 190. The non-divided column 190 can include a receiver 194 and areboiler 196.

Generally, the dividing wall column 100 can receive a feed 400 that mayinclude a plurality of naphtha components. The feed 400 can provide anoverhead stream 410 including a light naphtha, a side stream 420including a middle naphtha, and a bottom stream 460 that can include anaromatic and a heavy naphtha. Generally, as the feed 400 enters thecolumn 100, the lighter material can pass as the overhead stream 410passing through the overhead condenser 140 and then to the receiver 150.A part can be returned as a reflux 414 and another part may be withdrawnas a light naphtha product 418 from the receiver 150. A part of thebottom stream 460 can be provided as a feed 468 to the second column 190with another part as a return 464 to the column 100. Generally, thereturn 464 can pass through the reboiler 170 before entering the column100. In addition, a side draw 440 can be withdrawn from the column 100,passed through the side reboiler 180, and returned to the column 100.Generally, any suitable heating stream 450, as described above, can beused to first heat the reboiler 170, usually having a higher dutyrequirement, before being passed to the side reboiler 180. The feed 468can enter the second column 190. Lighter materials can exit as anoverhead stream 470 passing through an overhead condenser 192 beforeentering the receiver 194. A part can be returned as a reflux 474 withanother part withdrawn as an aromatic naphtha product 478. The heaviermaterial in the column 190 can pass out as a bottom stream 480 with aportion taken as a heavy naphtha product 488 and another part as areturn 484 to the column 100 which passes through the reboiler 196.

In embodiments discussed above, a single cooling stream can pass inseries through the overhead condenser 140 and then the side condenser160, and/or a single heating stream can pass in series through thereboiler 170 and then the side reboiler 180. Alternatively, coolingstreams and/or heating streams may be used separately in parallel. As anexample referring to FIG. 1, the system 10 can use separate streams,independently including any suitable fluid, such as air, water oranother process stream, to pass through the overhead condenser 140 andthe side condenser 160. Similarly, the system 10 can use separatestreams, independently including any suitable fluid, such as highpressure steam, medium pressure steam, low pressure steam, or anotherprocess fluid, to pass through the reboiler 170 and the side reboiler180. In one exemplary version, a high pressure steam can provide heatduty to the reboiler 170 and a hot light cycle oil stream can provideheat duty to the side reboiler 180. As such, the amount of high pressuresteam, which can be an expensive utility in a refinery or a chemicalmanufacturing unit as compared to other heat sources, can be reduced.

Without further elaboration, it is believed that one skilled in the artcan, using the preceding description, utilize the present invention toits fullest extent. The preceding preferred specific embodiments are,therefore, to be construed as merely illustrative, and not limitative ofthe remainder of the disclosure in any way whatsoever.

In the foregoing, all temperatures are set forth in degrees Celsius and,all parts and percentages are by weight, unless otherwise indicated.

From the foregoing description, one skilled in the art can easilyascertain the essential characteristics of this invention and, withoutdeparting from the spirit and scope thereof, can make various changesand modifications of the invention to adapt it to various usages andconditions.

1. A system for separating a plurality of naphtha components,comprising: A) a column, comprising: 1) a dividing imperforate wall withone surface facing a feed and another surface facing at least one sidestream wherein the wall extends a significant portion of the columnheight to divide the portion into at least two substantially vertical,parallel contacting sections; 2) an overhead condenser receiving anoverhead stream comprising a light naphtha from the column; and 3) aside condenser receiving a process stream from the column and returningthe stream to the column to facilitate separation; wherein a coolingstream passes through the overhead condenser and then the sidecondenser.
 2. The system according to claim 1, wherein the columnfurther comprising: a reboiler receiving at least a portion of a bottomstream and returning that portion to the column; and a side reboilerreceiving another process stream from the column and returning theanother process stream to the column.
 3. The system according to claim2, further comprising a heating stream passing through the reboiler andthen the side reboiler.
 4. The system according to claim 1, wherein theat least one side stream comprises a first side stream comprising amedium naphtha and a second side stream comprising an aromatic naphtha.5. The system according to claim 2, wherein the bottom stream comprisesa heavy naphtha.
 6. The system according to claim 1, wherein the coolingstream comprises cooling water.
 7. The system according to claim 3,wherein the heating stream comprises high pressure steam.
 8. A systemfor separating a plurality of naphtha components, comprising: A) a firstcolumn, comprising: 1) a dividing imperforate wall with one surfacefacing a feed and another surface facing a side stream wherein the wallextends a significant portion of the column height to divide the portioninto at least two substantially vertical, parallel contacting sections;2) a reboiler; and 3) a side reboiler; wherein a heating stream passesthrough the reboiler and the side reboiler; and B) a second columncommunicating with the first column so as to provide a feed to orreceive a feed from the first column wherein the second column isnon-divided.
 9. The system according to claim 8, wherein the heatingstream comprises a light cycle oil.
 10. The system according to claim 8,wherein the first column further comprises an overhead condenser and aside condenser wherein a cooling stream passes through the overheadcondenser and then the side condenser.
 11. The system according to claim10, wherein the cooling stream comprises cooling water.
 12. The systemaccording to claim 10, wherein the first column provides an overheadstream comprising a light naphtha.
 13. The system according to claim 10,wherein the first column provides a side stream comprising a mediumnaphtha.
 14. The system according to claim 10, wherein the second columnprovides an overhead stream comprising an aromatic naphtha.
 15. Thesystem according to claim 10, wherein the second column provides abottom stream comprising a heavy naphtha.
 16. A process for utilizingstreams for a plurality of vessels communicating with a divideddistillation column, comprising: A) passing a heating stream through areboiler and the same or a different heating stream through a sidereboiler to reduce the duty required in the reboiler of the divideddistillation column producing at least two of a light naphtha, a mediumnaphtha, an aromatic naphtha, and a heavy naphtha.
 17. The processaccording to claim 16, further comprising passing a cooling streamthrough an overhead condenser, and then a side condenser of the divideddistillation column.
 18. The process according to claim 16, wherein theheating stream comprises pressurized steam.
 19. The process according toclaim 16, wherein the heating stream comprises light cycle oil.
 20. Theprocess according to claim 16, wherein the heating stream for thereboiler and side reboiler is the same.